Heat Capacity of Pb10 –xPrx(GeO4)2 +x(VO4)4– x (x = 0, 1, 2, 3) Apatites in the Range 350–1050 K

Synthesis, Crystal Structure and Thermodynamic Properties of Apatite-like Lead Gadolinium Vanadato-germanates

“…Апатиты, обладая уникальными физико-химическими свой ствами, уже в течение длительного времени привлекают к себе внимание исследователей и практиков [1][2][3][4][5][6][7][8][9][10]. Они используются в качестве биоматериалов, лазерных, люминесцентных и оптических материалов [3,11].…”

“…Подобная замена части свинца на висмут позволила получить апатиты составов Pb 10-x Bi x (GeO 4 ) 2+x (VO 4 ) 4-x (x = 0-3) [13]. Замещением свинца на празеодим получены соединения Pb 10-x Pr x (GeO 4 ) 2+x (VO 4 ) 4-x (x = 0 -3) [6,10]. В отличие от хорошо известного гидроксиапатита [4, 14 -16] его свинцовые аналоги исследованы недостаточно [6].…”

Synthesis, crystal structure and thermodynamic properties of apatite Pb-=SUB=-3-=/SUB=-Bi-=SUB=-2-=/SUB=-(GeO_4)-=SUB=-3-=/SUB=-

“…For example, replacing lead in apatite Pb 5 (GeO 4 )(VO 4 ) 2 with rare earth elements enabled to obtain Pb 10−x R x (GeO 4 ) 2+x (VO 4 ) 4−x (R = La, x = 2 [15]; R = Pr, x = 2 [6], x = 0−3 [16]; R = Nd, x = 0−3 [6]) and with bismuth -…”

Synthesis, crystal structure and high-temperature heat capacity of substituted apatites Pb-=SUB=-9-=/SUB=-R(GeO-=SUB=-4-=/SUB=-)-=SUB=-3-=/SUB=-(VO-=SUB=-4-=/SUB=-)-=SUB=-3-=/SUB=- (R=Tb, Dy, Ho)

“…Such a substitution allows both for changing the properties of the already known compounds with the apatite structure and for making new materials [16,17]. Thus, for instance, partial substitution of lead in apatite Pb 5 (GeO 4 )(VO 4 ) 2 (or Pb 10 (GeO 4 ) 2 (VO 4 ) 4 ) by rare earth elements (REE) provides compounds with the general formula Pb 10−x R x (GeO 4 ) 2+x (VO 4 ) 4−x (Rrare earth element, x takes on values from 0 to 3) [13,[18][19][20][21][22][23][24][25], and by bismuth -Pb 10−x Bi x (GeO 4 ) 2+x (VO 4 ) 4−x [26]. It should be noted that the properties of apatites Pb 10−x R x (GeO 4 ) 2+x (VO 4 ) 4−x have been poorly studied, while the available data mainly pertains to epy studies of their crystal structure.…”

“…We have obtained the heat capacity data only for the apatites of this class which contain La [19,20,22,25], Pr [23,25], Nd [21,25], Eu [24], Sm [25]. The available published data about thermodynamic properties pertains to other compounds with the apatite structure (fluor-, chlor-and hydroxyapatites) [27,28].…”